1. Field of the Invention
The invention relates to an electric motor driving device and a vehicle equipped with the same and, more particularly, to an electric motor driving device for driving an electric motor that is able to regulate the armature winding flux linkage.
2. Description of the Related Art
In recent years, as an environmentally friendly vehicle, a vehicle that is equipped with an electrical storage device (for example, a secondary battery, a capacitor, or the like) and that is propelled by driving force generated from electric power stored in the electrical storage device becomes a focus of attention. Such a vehicle, for example, includes an electric vehicle, a hybrid vehicle, a fuel cell electric vehicle, and the like. Then, there is a suggested technique for charging an electrical storage device equipped for these vehicles using a commercial power supply having a high power generation efficiency.
These vehicles may be provided with a rotating electrical machine (motor generator) that generates driving force for propelling the vehicle with electric power supplied from the electrical storage device at the time of start or acceleration and that generates electric power through regenerative braking during braking to store electric energy in the electrical storage device. In this way, in order to control the motor generator in response to a running condition, the vehicle is equipped with an inverter. In such a vehicle, electric power required by the inverter varies depending on a vehicle state. Then, in order to stably supply electric power required by the inverter, a converter may be provided between the electrical storage device and the inverter. The converter raises the input voltage of the inverter from the output voltage of the electrical storage device to achieve a high-power motor, and reduces a motor current with the same power to thereby make it possible to reduce the size and cost of the inverter and motor.
In addition, a permanent-magnet motor, a field winding motor, and the like, are considered as the rotating electrical machine used for such a vehicle. The permanent-magnet motor rotates by magnetic action between magnetic poles of a permanent magnet provided for a rotor and a rotating magnetic field that is generated in a stator. The field winding motor rotates by magnetic action between a component, vertical to a rotary shaft, of magnetic field that is generated in a rotor equipped with a field coil by flowing field current to the field coil and a rotating magnetic field that is generated in a stator.
Japanese Patent Application Publication No. 2008-228534 (JP-A-2008-228534) describes an electric motor driving device that is configured to be able to regulate the armature winding flux linkage of an electric motor in such a manner that a reactor of a step-up converter also serves as a field winding of the electric motor and a switching element connected in parallel with the reactor is controlled for switching.
With the electric motor driving device, the armature winding flux linkage may be varied in accordance with the state of the electric motor, so it is possible to reduce the size of the driving device and increase the power of the electric motor.
However, in the configuration described in JP-A-2008-228534, the power of the electric motor may be increased when the electric motor is driven in a power running mode; however, it does not consider increasing the power of the electric motor when the electric motor is driven in a regeneration mode. Therefore, there is a possibility that the power of the electric motor is decreased adversely during regeneration.